1. The Generic Pixel Server (GPX) Dictionary
A common command set for image acquisition
N. C. Buchholz
P. N. Daly
(NOAO)
Copyright, 2004 © AURA, Inc.

2. Introduction Background The Goal GPX Communications GPX Command Set
Attribute-Value Pairs
Image Data Handling
Future Developments

3. Background
Nov ACCORD conference outlines GPX concept, Santa Cruz, CA
Feb GPX definition proposed at AURA Software Conference, Baltimore, MD
Mar MONSOON Software Design started, NOAO, Tucson, AZ
Aug.- Sep First light on MONSOON Systems, Tucson, AZ & La Serena, Chile

4. MONSOON Team
August, 2003
L to R: Peter Moore, Dee Stover, Paul Schmitt, Dave Dryden, John Garcia, Jerry Penegor, Nick Buchholz, Phil Daly and Dave Sawyer. (Not shown: Gustavo Rahmer, Mike Warner, Ricardo Schmidt, Mark Hunten).

5. MONSOON Results 8 August 2003: First Light Aladdin_III
19 September 2003: First Light Hawaii II
29 September 2003: First Light CCD

6. The Goal
Astronomical images as easy as digital photography

7. The MONSOON Image Acquisition System
An Extensible architecture.
Defined by Interface Control Doc’s at each level.
Based on COTS Technology and a small number of reusable in-House boards.
Not tied to a specific hardware set.
Designed for large pixel count detectors & Mosaics.
IR FPAs, CCDs, OTAs, Allows for digitizing Focal Planes.
Allows for re-packaging of electronics.
Three Level System.
MSL - Single control point for the entire focal plane.
PAN - Intelligence for a section of the focal plane.
DHE - Low-level Hardware control for a section of the focal plane.

8. The MONSOON Image Acquisition System

9. The Generic Pixel Server (GPX)
Isolates focal plane control from:
Telescope control.
Instrument mechanism and temperature control.
Data archiving (the DHS mechanisms).
User GUI’s and Status displays.
Significantly reduces the complexity of the software.
No functionality is lost.

10. GPX Communications Simple socket-based communications.
Bi-directional message based.
Multiple connections permitted.
ASCII text based commands & responses.
Small number of fixed formats.
Designed for simple response parsers.
Provides for Unique command id.
MONSOON Uses - MONSOON Star Date (MSD) - accurate (to 1s) time stamp based upon Julian day plus gettimeofday() function.
Interface calls for 8 ASCII bytes for ID.

11. GPX Communications (Cont.)
Provides for asynchronous event handling.
Power glitches, spurious resets.
Communications failures.
Detector voltage changes.
Exposure completion.
GPX system can require asynchronous event response.
Insures Client software catches events.
Allows info only events (for status reporting).

12. GPX Command Set - System Set-up.
gpxSetMode - general purpose set-up command.
Set-up selection is by mode name.
<SAVE> allows automated mode creation.
gpxSetMemCfg - DHE Memory configuration.
Loads memory addresses without error checking.
Used for waveform sequencer program & patterns.
gpxSetAVP - Set Attributes to desired values.
PAN checks for value range errors.
PAN checks for data lock-outs.
Redundant commands - add convenience.
gpxSetArrCfg, gpxSetExpCfg, gpxSetIdpCfg.

13. GPX Command Set - Exposure Control.
gpxStartExp - starts an exposure sequence.
All PAN/DHE pairs synchronized by hardware.
Controls local shutter if available.
Handles integration timing
accuracy determined by DHE hardware.
gpxWaitForTrigger - arms the DHE sequencer
Same functionality as gpxStartExp
Sequencer waits for hardware trigger signal.
gpxPauseExp, gpxResumeExp -
May be NO-OPs for certain systems (IR FPAs)
gpxStopExp, gpxAbortExp

14. GPX Command Set - Info, Status & State.
gpxGetState - reports the state of the PAN/DHE.
Response determines range of allowed actions.
gpxGetAVP - reports the value of an Attribute.
Directives allow range and permission checking.
Return could report value out-of-range as well.
gpxAsyncMsg - unsolicited message reporting event.
May require response from upper level.
Built-in to several levels of system.
gpxAsyncResp - upper level response to gpxAsyncMsg.

15. GPX Command Set - Hardware Controls
gpxPower - control for power to GPX systems.
Systems may elect not to provide this control.
Can be used to control voltages to detector.
gpxReset - multi-level system reset .
Provides board level warm and cold re-start.
Provides Fiber channel reset, DHE reset, possible PAN process reset.
gpxShutter - sets local shutter control state.
Normally sets shutter state for subsequent exposures.
immediate directive (<IMMD>) controls shutter NOW.
gpxShftImg - send an image shift command to DHE.
provided for control of OTAs and Shift-and-Add systems.

16. GPX Command Set - Miscellaneous
Debug and Test
gpxDebug, gpxSimulate, gpxTestMode
gpxPass
Meta-Commands
gpxHelp, gpxDump
gpxExit, gpxShutdown
GPX Client Library
connectGPX, disconnectGPX,
sendGPX, recvGPX
asyncRespGPX

17. Async Messages and Responses
Used to deal with asynchronous or unexpected events.
Available at each interface level.
Allows synchronization between levels. (rendezvous.).
Allows automated error recovery.
Allows Client/upper levels to act on low level events.
No additional out of band protocol required.

18. Future Developments
Complete additional “Use-Case” reviews to insure the Dictionary is complete.
Complete NOAO ICD 4.1 to describe the MONSOON implementation of the GPX.
Complete the description of the Status Reporting and DHS interface libraries.
Use the GPX dictionary to complete the implementation of NEWFIRM, IR and CCD LAB, OTA test, Science & Engineering Client systems.
Complete Implementation of the Client-GPX Interface Library.

19. Papers at SPIE ...
N. C. Buchholz and P. N. Daly, “The MONSOON Generic Pixel Server Software Design”,
P. N. Daly and N. C. Buchholz, “The MONSOON Implementation of the Generic Pixel Server”,
P. N. Daly, N. C. Buchholz and P. C. Moore, “Automated Software Configuration in the MONSOON System”,
N. C. Buchholz and P. N. Daly. “The Generic Pixel Server Dictionary”,
R. G. Probst, N. Gaughan, G. Chisholm, P. N. Daly, E. A. Hileman, M. Hunten, M. Liang, K. M. Merrill and J. Penegor, “Project Status of NEWFIRM: the Wide-field Infrared Camera for NOAO 4m Telescopes”,